Aquatics & Recreation Specialist Guide to Ph and Alkalinity

Andrew
Feb 7, 2018
6 min read

Contributor: Ivana Stojkovic

This guide is intended to be a basic introduction for individuals looking to operate their commercial swimming pool more effectively. Operators MUST take a CPO course to learn more.

Audience:

Pool Managers
Property managers
Aquatic managers
Lifeguards
Recreation professionals

What you'll learn

Why pH is the king of pool chemistry
The pH scale
Why you should correct alkalinity, then pH then chlorine
How pH works most effectively with chlorine
Why low and high pH is bad for swimmers and pool equipment
How often to check alkalinity and pH

TAKE THE QUIZ AND GET A CERTIFICATE OF COMPLETION

Introduction

Like many people reading this, i focused mostly and firstly on chlorine for many years as an operator. I was concerned with,

Getting chlorine levels above 1ppm for good record keeping
passing a health dept inspection
Avoiding algae growth

It took me a long time of working with experienced professionals and visiting hundreds of pools and seeing the problems they were having to understand the importance of pH and Alkalinity and addressing pH first that helped me get better results in operating commercial swimming pools.

pH - The King of Pool Chemistry

What is pH?

For the purposes of this basic course pH is a measure of how acidic or basic water is.

The range goes from 0 - 14, with 7 being neutral.

You don't need to know the exact science all you need to know is the,

pH scale

pH alone is unstable.

Rainwater, swimmers, and just about anything that enters the water can affect the pH level. When pH is low, it means your water is acidic, and when it’s high, you water is basic.To give you an idea of how pH works, our tears are pH neutral. If they had a low pH, it would burn when we cried. And if the pH was high, it would dry out our eyes.

It is important to know that the Ph scale is logarithmic. This means that a reading of 6 is 10x more acidic than a reading of 7 and a reading of 5 is 100x more acidic than 7.

pH and water balance in pools

Pool water balance is very important. It can be defined as the relationship between different chemical measurements in your pool water. Everything from weather to oils, dirt, and cosmetics can affect pool water balance. In short, anything that comes in contact with your pool water.

Extremely high and low pHs can be detrimental for

Swimmers
Pool surfaces
Pool equipment

High pH (above 8) causes a bitter taste of water,

chlorine activity is slowed and inefficient.
There is scale formation and discoloration of pool walls.
Water becomes cloudy.
Filters are overworked and may become clogged, slowing flow.
Also, eye and skin irritation may occur.

A low pH (below 7) gives aggressive, corrosive water, which

damages the mechanical components of the pool.
It damage the pool liner.Cause irritations of the eyes and mucous membranes.

Why is Ph so important?

pH is a very important measurement of water quality. Since pH can be affected by chemicals in the water, it is also an important indicator of water that is changing chemically. As mentioned before, pH is the most important element in swimming pool water chemistry. It affects every other chemical balance in the pool. pH level is, in many ways, the foundation of pool water balance.

pH and its big brother TOTAL ALKALINITY, are the most important for maintaining pool water in balance.The importance and roles of pH and alkalinity are often not well understood even by veteran pool owners.

There are many factors that can impact pH level, but with a little practice and regular attention, you can ensure that your water stays in the range that is ideal for your pool equipment and perfect for pool users.

pH and Alkalinity

Total alkalinity, as already mentioned, is not the same as pH but is closely related and affects the pH stability. Ideal Alkalinity levels prevent pH BOUNCE and pH LOCK.

Think of Alkalinity as an anchor and pH as a boat. When swimmers,chemicals and environmental conditions ‘crash’ against pH the correct alkalinity range will hold Ph steady and it prevents rapid pH changes.

If alkalinity is too high, water pH could drift to an extremely high level very easily, and it can be difficult and slow to get it back down to normal. If the alkalinity is too high, there may be signs of scaling and very cloudy pool water.

If alkalinity is too low, it will be very hard to control the pH. pH is bouncing, rapidly going up and down, seemingly at random. Low alkalinity pool water can be very corrosive, eating away at pool surfaces and the pool equipment.

It is important to remember to adjust alkalinity FIRST and then the pH in the pool water.

For BEST pH consistency, Alkalinity should be maintained in the 80-120 parts per million (ppm).

pH and chlorine

Chlorine, the most popular disinfectant and sanitizer, works more effectively in low Ph conditions. Equally the same amount of chlorine will have less ‘bacteria killing power’ in high Ph conditions

In most commercial swimming pools chlorine is constantly fed into the pool either manually or automatically and will affect the Ph throughout the operating day.

Not all chlorine products are the same and you should be aware how the particular disinfectant YOU use will affect pH

For example,

Sodium Hypochlorite(bleach) has a pH of 11-13 so it will RAISE pH

Tri chlor (stabilized chlorine) has a pH of 3 so it will LOWER pH

Testing pH and Alkalinity

The optimum pH for pool water is7.4, since this is the same as the pH in human eyes and mucous membranes. A pH of 7.4 also gives good chlorine disinfection.

pH should be tested at least once daily and is recommended to be tested 2-3 times daily at logical intervals, especially for high usage commercial pools

When Alkalinity levels are within range It is recommended that alkalinity is measured once a week.

Pool pH and algae growth

Phytoplankton, or water algae constantly enters the pool, brought in by wind, rain, contaminated swimsuits or even pool cleaning tools. It is interesting to notice, that algae is always present in swimming pools, even in clean and blue pools, at a microscopic size. They wait patiently for the opportunity to bloom such as,

High ph
Warm temperatures
Sunlight
Increase in phosphates, nutrients and minerals
Poor circulation due to dirty filters

Pool algae prefers a higher pH of 8.0 or above. High pool pH won’t necessarily cause algae growth, but it does have the effect of reducing the efficacy of chlorine.Algae blooms however, can raise the pH of your pool water. Because of photosynthesis, they produce enough oxygen in the water to raise pool pH levels, especially at the end of a warm, sunny day.

How to raise ph in the pool

If after testing pool water, shows that the pH is too low (below 7.2), there are few techniques to raise pH.

Add Sodium Bicarbonate (baking soda). This raises both pH and Alklinity and is the preferred chemical to add to raise pH.

Add 1.4 lbs of sodium bicarbonate also called baking soda per 10,000 gallons of water in pool. This should raise the total alkalinity by 10 ppm. Again, let the water circulate for an hour or more before testing again.

2. Add soda ash.

It’s important to remember never to add more than 2 lbs of soda ash per 10,000 gallons of water in your pool in any single treatment. Distribute the soda ash over the whole of the pool surface, while the pump is circulating and wait an hour or so before testing again. If the pH is still too low after an hour, more soda ash can be added. Soda ash may cloud the pool water, but this should fade out within a day or so.

How to lower ph in pool

If after testing pool water, shows that pH level is too high (above 7.8), you can determine what you need to lower that value.

The Most commonly used chemicals to decrease pH in pools are,

Muriatic acid - most common type of liquid which has a strong odor.
Sulfuric Acid - a non fuming liquid which may not lower alkalinity as much as muriatic acid.
Dry Acid - come in granular form in containers, with names like ‘’pH Minus’’, ‘’pH Reducer’’ or ‘’pH Decreaser’’.

No matter which chemical is used to lower pH, it is important to read the instructions on the label and stick to them, FOR YOUR SAFETY.

Ph and Automatic Controllers

Automatic controllers monitor and automatically feed sanitizer and acid when the ideal range is lower or higher.

for example , when the pH goes above the ideal range of 7.5.

In order for Automatic controllers to be reliable it is critical that Alkalinity is kept between 80-120 consistently.

When the Alkalinity is below 80 the pH swings erratically increasing or decreasing the effectiveness of the Chlorine (ORP). pH bounce will drift the pH reading away from the real pH of the water and require your controller to be re-calibrated.

TAKE THE QUIZ AND GET A CERTIFICATE OF COMPLETION

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